Fuel cells produce direct electrical current and electrolysis cells ordinarily use direct electrical current. Therefore, it is desirable to direct and close couple electrically a fuel cell with an electrolysis cell to avoid the electrical losses associated with rectification as well as to avoid the electrical line losses associated with the usual conventional commercial electrical power utilization of fuel cells with electrolysis cells. This conventional utilization is accomplished by conversion of the fuel cell's electrical output from D.C. to A.C. current into a commercial power grid, transmission of some of the A.C. electrical current of the grid to the electrolysis cell site, and reconversion of this A.C. electrical current to D.C. electrical current at the electrolysis cell site for use by the electrolysis cell.
Many attempts have been made at direct coupling of fuel cell stacks to electrolysis cells. However, such direct coupling produces stability problems for the fuel cell's electrical output. This is brought about because the characteristics of the fuel cell cause it to produce less voltage at higher amperage outputs while the characteristics of the electrolysis cell require a higher voltage for a corresponding increase in current. Likewise the fuel cell produces a higher voltage if a lower current is demanded of it while an electrolysis cell needs a lower voltage for a lower current.
Consequently, a perturbation in the current in the electrolysis cell would ordinarily produce a runaway instability problem in the fuel cell's electrical output. For example, a sudden increase in the current passing through the electrolysis cell would require a sudden increase in the current output of the fuel cell. But these two like current changes call for opposite changes in the voltages of the electrolysis cell and the fuel cell. The fuel cell's voltage would ordinarily tend to decrease while the electrolysis cell's voltage would ordinarily tend to increase or at least stay the same. However, nature will not allow this to happen in the direct electrical current coupling desired between the fuel cell and the electrolysis cell. The present invention overcomes this stability problem.